1. Field of the Invention
This invention relates to a milking system having a milking apparatus for connection with a cow's teats to apply a controlled vacuum to the end of the teats to remove milk therefrom in combination with a novel and unique milk claw and more particularly relates to a milking system having a milking claw with an outlet and a milk transportation conduit wherein the predetermined cross-sectional area of each of the milk claw outlet and the milk transportation conduit components including the milk line is selected to be within a minimum and maximum range for maintaining, at all flow rates, a substantially uniform laminar flow of milk therethrough and for concurrently providing a stable continuous vacuum in a vacuum channel between the laminar flow of milk and the interior side walls of the milk claw outlet and milk transportation conduit.
2. Description of the Prior Art
Milking systems having a vacuum for performing milking of cows are well known in the art. Examples of such milking systems and controls therefor are described in several United States Patents.
U.S. Pat. No. 4,947,793 discloses a method and apparatus for measuring milk yield from an animal which has been milked using milking machinery. The milking machinery disclosed in U.S. Pat. No. 4,947,793 includes a valve which is operative to extract milk with minimum entrained air from the milking claw at a substantially constant pressure differential across the seat of the valve. The milking apparatus includes a detection and timing mechanism in which in use the apparatus detects the periods during which the valve is open and records the total time during a milking of an animal. The apparatus further includes a mechanism which translates the total time the valve is open into a measurement which indicates the yield of milk from the animal.
U.S. Pat. No. 4,616,215 discloses a vacuum monitoring apparatus which includes a control circuit having a transducer for sensing the vacuum levels in a milking system and for generating output signals. The control circuit includes a comparator for controlling indicator devices and an alarm circuit in response to a set point when the vacuum levels are at high, low and normal settings. The control circuit includes a time delay circuit that disables the alarm circuit for a predetermined time delay to provide for measurement of the vacuum recovery rate for the system.
U.S. Pat. No. 4,605,040 discloses a partial-vacuum regulating valve that automatically regulates an operating partial vacuum in milking systems. The partial-vacuum regulating valve consists of a main valve and an auxiliary valve. The auxiliary valve body is adjusted in accordance with the partial vacuum prevailing in the milking system and affects the amount of air that is drawn out of the main valve control chamber, which communicates with the atmosphere through a calibrated bore, through a certain channel. The partial-vacuum is adjusted in the control chamber in accordance with the amount of air drawn out and that adjustment determines the position of the auxiliary valve. The position of the auxiliary valve determines the amount of air flowing into a certain line through the air-inlet opening, which in, turn, affects the partial pressure in the line. The main-line control chamber has an additional calibrated air inlet that is closed off with a cap. When the cap is removed, atmospheric air also flows through the additional inlet into the main valve control chamber and reduces the partial vacuum therein. The associated descent of the valve body reduces the air admitted onto the line and hence leads to partial pressure in the milking system that is lower than the partial pressure established for the milking process by means of a screw and spring.
U.S. Pat. No. 4,572,104 discloses a method of milking for a double action milking system. Milking is initiated at one ratio of milk period and then increased to a selected higher ratio. Milking is then done at the selected higher ratio for a selected segment of time or until the milk flow rate falls below a predetermined value, after which the ratio is decreased so that milking is completed at a lower ratio. A valve is used to selectively alternatively connect a line going to the teat cups to vacuum or to atmospheric pressure.
U.S. Pat. No. 4,516,530 discloses an automated milking system in which the milking vacuum applied from a vacuum line through a milk flow valve and the milk hose to a teat cup cluster is initially shut off after automatic detacher controls provide a signal indicating the end of milking. A milk sweep controls a backflush system which passes a flushing fluid through the milk flow valve into the milk house and teat cup cluster to flush out these components.
U.S. Pat. No. 3,783,837 discloses a milking machine having a duct under partial vacuum that leads milk from the teat cup cluster to form a milk flow having a milking flow rate. The duct has a regulating valve which is used to vary the milking vacuum. A device for sensing changes in the rate of milk flow through the duct is connected to control means for operating the regulating valve to an idling value in response to a decrease in the milk flow rate and an increase in the milking vacuum from an idling value to a working value in response to an increase in the rate of milk flow.
U.S. Pat. No. 3,476,085 discloses an air vent plug adapted to be inserted in the wall of a milking inflation forming part of a teat cup cluster for improving the milk flow therethrough. The air vent plug includes a properly calibrated port in the plug for admitting a metered amount of air into the upper end of a milk tube portion of the teat inflation to push milk rapidly therefrom and prevents excessive pressure from being exerted on the teat orifice.
A reference entitled MACHINE MILKING AND LACTATION by A. J. Bramley, F. H. Dood, G. A. Mein and J. A. Bramley, published by Insight books, Vermon, USA, describes the history, background and state of the art in milking systems and in Chapter 7 entitled Basic Mechanics and Testing of Milking Systems by G. A. Mein appearing at Pages 235 through 284, discloses and describes typical milking machine installations (the "Bramley et al. Reference"). The Bramley et al. Reference recognizes that controlling the maximum vacuum drop in the system is desirable because the vacuum drop depends on surface finish of pipes and the overall effective length, including bends and fittings of piping in the milking system.
It is known in the art that mastitis can occur if a milk blockage occurs within the inflation of a teat cup cluster causing a back flow of milk into the teat's orifice. Mastitis is an infection of animal body tissue within the mammary system of an animal. Mastitis may be caused by a number of other conditions including irritation to the teats, as is well known to persons skilled in the art. In a milking process, mastitis is generally caused by an introduction of foreign bacteria into the animal's udder, e.g. cow's udder, caused by severe irritation to the teats such that the teat orifices cannot be protected from environmental bacteria entering the teats. When mastitis occurs, it is an infection that the animal, e.g. cow's, body must counteract. Thus the animal's body energy is to be used to fight infection rather than produce milk.
If the infection is severe enough, significant and sometimes permanent damage can be caused to the cow's normal milk producing organisms. All mastitis cause some level of permanent and lifetime irreputable damage to the animal's milk producing (mammary) system. The level of severity is in direct relation to the severity and length of time that an infection exists. As such, a severe or lengthy period of infection may limit the animal's production capabilities and affect the animals milk producing life.
A milking machine or milking system generally cause mastitis in two ways.
First, mastitis is caused by application of damaging vacuum levels to the cows' teats which create a severe irritation. Since it is difficult to isolate with any degree of certainty at what level of vacuum such irritation occurs, the conservative approach is the least level of vacuum, the better. Each animal, such as a cow, reacts differently to vacuums being applied to teats and each animal tolerates various levels of vacuum differently.
Second, mastitis is created by a milking apparatus, causing foreign bacteria to be introduced into the animal, e.g. cow. As milk is being drawn from the cow, the teats are exposed to a vacuum which is less than atmospheric pressure. However, the outside of the udder is under atmospheric pressure and, in essence, atmospheric pressure is what is "squeezing" the milk out of the animal's teats in response to a periodic pulsating or controlled vacuum from a pulsator.
When vacuum is applied to an animal's teats, a lower than atmospheric pressure exists within the animal's udder. When the animal gives milk faster than the milking system can transport the milk away from the teats resulting in a blocking or interfering with the vacuum, a flooding situation occurs resulting in the vacuum being blocked from the teats and udder. The udder is under the operating vacuum level equal to the source before the flooding occurs when flooding occurs, an at atmospheric pressure is bleed into the milk claw. The vacuum level within the milk claw drops because the flooding blocks the source of vacuum from the milk claw. This results in the loss of vacuum to the teats and udder. The udder seeks to return to the ambient atmospheric pressure from the original vacuum level. As a result, air will then fill the vacuum. The filling of the vacuum within the cowl's udder causes a foreign air to be introduced into or drawn into the cow's udder. Air does not typically carry a detrimental amount of foreign bacteria, but air under a pressure differential functions as a propellant for bacteria. As such, air itself does not cause significant detriment to the health of the animals, e.g. cow, but the air may transport bacteria or other contaminants into the teats.
Another phenomenon exists that is detrimental to the animal. The liner of the milking apparatus or inflation creates a seal between atmospheric air outside the cow from the vacuum which is at lower than atmospheric air inside of the inflation and ultimately into the cow's udder. Typically, the inflation is sealed around the cow's udder by body flesh. The cow's udder is always contaminated with bacteria because of the animal's environment. Most often, the animal is only washed before milking. Since only water is used to wash the udder and the udder is not sanitized, water typically is a carrier of bacteria from outside of the udder.
If the vacuum seal breaks and water carrying bacteria is present around the udder, the water outside of or in the vicinity of the inflation and air at atmospheric pressure is drawn or sucked into the teats through the teat orifice.
To overcome such prior art, the inflations and milking systems have been designed to resist breakage of the vacuum seal. Also, sanitizers have been developed to sanitized the cow's udder before milking. Further, milk claws have been designed to direct air, milk, water or other material away from the milk flow and away from the cow's teats to minimize the introduction or drawing of bacteria into the teat orifice.
As discussed above and as shown by the prior art, animals, such as cows, are being milked with greater and greater vacuum levels in order to decrease milking times and to form a tighter seal around the inflation and cow's teat to reduce "squawking", e.g. air admission into the test created by a broken vacuum seal.
It is known in the art that higher levels of vacuum, although helping in decreasing the milking time, also cause irritation to the animal and are undesirable to overall animal's health and mammary system. Nevertheless, many milking systems have increased vacuum to reduce milking time and to reduce "squawking". Such milking systems have done so by forfeiting the advantages of less irritation associated with lower vacuum levels.
Typically, animals, especially cows, are giving more milk at faster milk flow rates. The sizes and design of the state-of-the-art entire milking system are generally inadequate to handle the volume of milk without some degree of, and often severe, flooding. Flooding continually causes reverse pressure differentials and collapse of vacuum. The milk fluid, in effect, causes the average vacuum level within the claw, liners and teat end to be much lower than the desired vacuum level due to continual flooding which interrupts the vacuum and causes undesired pressure differences on the teats. The present predominate solution is to continue to raise and/or dynamically change the vacuum levels.
It is important to note that the "average" vacuum level used to milk a cow is lower than that of the preset vacuum level of the vacuum source. However, at times when the cow is not giving milk at a fast rate, the cow is being exposed to the differential in pressure between the higher levels of vacuum. Several of the known milking systems and apparatus include valves, control means or the like to control vacuum levels as a function of milk flow rates as a means to solve such problems.